Self expanding stents are used in coronary and peripheral vascular as well as endovascular applications. Specific vessels in which stents may be implanted include coronary arteries, renal arteries, peripheral arteries including iliac arteries, arteries of the neck and cerebral arteries, veins, biliary ducts, urethras, fallopian tubes, bronchial tubes, the trachea, the esophagus and the prostate.
Stents are available in a wide range of designs. Typically, stents are either mechanically expandable or self-expanding. Mechanically expandable stents are usually expanded with a balloon. An example of a mechanically expandable stent is a stent made from stainless steel. Self-expanding stents expand either as a result of a transformation of the material or because of the energy which has been stored therein. Examples of the former include stents made from shape memory materials including shape memory metals such as Nitinol and shape memory polymers. Examples of shape memory stents include Nitinol stents. Hybrid stents exhibiting properties of both self-expandable and mechanically expandable shaft are also known.
In use, stents are typically disposed about a delivery device and delivered to a desired location in a bodily vessel where they are then either allowed to self-expand or where they are mechanically expanded. Mechanically expanded stents are usually delivered on a balloon catheter. A stent is disposed about a balloon and at the desired time, the balloon is inflated with an inflation fluid. The expansion of the balloon, in turn, applies an outward force to the stent to expand the stent.
Self-expanding stents are typically plunged into a sheath in the form of a polymer tube on the delivery device. This maintains the stent in a reduced diameter configuration. At a desired time, the sheath is withdrawn, allowing the stent to self-expand. This reduced diameter enables the stent to be tracked to and access a given treatment site where the sheath is then retracted off the stent, allowing the stent to expand and oppose the vessel wall.
As the state of the art develops, self expanding stents in particular and self-expanding medical devices in general are trending toward larger and longer sizes. Also there is an increased effort toward development of drug eluting self expanding stents and other self-expanding medical devices.
With the trend toward longer and larger stents as well as drug coated stents and devices; there are complications with the current stent loading methods. For example, alignment becomes an issue with large diameter stents when trying to compress and load them in small sheaths. Also, frictional forces developed during loading increase with longer stents and may result in buckling of the stent or the sheath. The loading of a drug coated stent into a sheath can cause damage to the coating—especially on the longer and larger stent sizes. The various drug coatings can range from being brittle and poorly adhered to the stent material to being soft and of high tack relative to the stent material. Stent material may be, for example, Nitinol or stainless steel.
There remains a need for innovative methods for loading self-expanding stents and other self-expanding devices onto delivery catheters. There also remains a need for innovative devices which are capable of loading self-expanding stents and other self-expanding devices onto delivery catheters.
Without limiting the scope of the invention a brief summary of some of the claimed embodiments of the invention is set forth below. Additional details of the summarized embodiments of the invention and/or additional embodiments of the invention may be found in the Detailed Description of the Invention below.
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